Hydrophilic compositions, methods for their production, and substrates coated with such compositions

ABSTRACT

Liquid compositions are disclosed that include a photocatalytic material and a hydrophilic binder that includes an essentially completely hydrolyzed organosilicate. Also disclosed are methods of making such compositions, methods of coating a substrate with a hydrophilic composition, and substrates coated with such compositions. The compositions may, for example, be embodied as stable one-pack compositions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/575,437, filed May 28, 2004.

FIELD OF THE INVENTION

The present invention relates to liquid compositions that include aphotocatalytic material dispersed in a hydrophilic binder that includesan essentially completely hydrolyzed organosilicate. The liquidcompositions may be embodied as coating compositions. In particular, theliquid compositions may be employed as, for example, stable one-packcoating compositions that form hydrophilic and durable coatings that mayexhibit advantageous, easy-to-clean, self-cleaning, anti-fouling,anti-fogging, anti-static and/or anti-bacterial properties. Coatingsformed from such liquid compositions can be rendered super-hydrophilicupon photoexcitation of the photocatalytic material.

BACKGROUND OF THE INVENTION

Hydrophilic coatings are advantageous for certain coating applications,such as where coated surfaces exhibiting anti-fouling, easy-to-clean,self-cleaning, and/or anti-fogging properties are desired. Such coatingscan be particularly useful, by way of example, for application tosurfaces exposed to the outdoor environment. Building structures as wellas other articles that are exposed to the outdoors are likely to come incontact with various contaminants, such as dirt, oil, dust, and clay,among others. Rainfall, for example, can be laden with suchcontaminants. A surface with a hydrophilic coating deposited thereon maybe anti-fouling by preventing contaminants in rainwater from adhering tothe surface when the rainwater flows down along the coated surface.Moreover, during fair weather, air-born contaminants may come in contactwith and adhere to surfaces. A surface with a hydrophilic coatingdeposited thereon may be self-cleaning because the coating has theability to wash those contaminants away when the surface comes incontact with water, such as during a rainfall.

Coatings having self-cleaning and/or anti-fouling properties may also beadvantageous for application to surfaces that are exposed to indoorcontaminants, such as, for example, kitchen contaminants, such as oiland/or fat. An article with a hydrophilic coating deposited thereon canbe soaked in, wetted with, or rinsed by water to release contaminantsfrom the coating and remove them from the surface of the article withoutuse of a detergent.

Coatings having anti-fogging properties can be particularly useful inmany applications as well. For example, articles containing surfaceswhere visibility is important, such as windshields, windowpanes,eyeglass lenses, mirrors, and other similar articles can benefit from acoating with anti-fogging properties because they contain surfaces thatcan often be fogged by steam or moisture condensate or blurred by Waterdroplets adhering to the surface thereof. It is known that the foggingof a surface of an article results when the surface is held at atemperature lower than the dew point of the ambient atmosphere, therebycausing condensation moisture in the ambient air to occur and formmoisture condensate at the surface of the article. If the condensateparticles are sufficiently small, so that the diameter thereof is aboutone half of the wavelength of the visible light, the particles can causescattering of light, whereby the surface becomes apparently opaque,causing a loss of visibility.

A surface with a hydrophilic coating deposited thereon may beanti-fogging because such a coating can transform condensate particlesto a relatively uniform film of water, without forming discrete waterdroplets. Similarly, a surface with a hydrophilic coating depositedthereon can prevent rainfall or water splashes from forming discretewater droplets on the surface, thereby improving visibility throughwindows, mirrors, and/or eyewear.

In view of these and other advantages, various hydrophilic coatingcompositions have been proposed. Some of these coatings achieve theirhydrophilicity through the action of a photocatalytic material that isdispersed in a silicon-containing binder. For example, U.S. Pat. No.5,755,867 (“the '867 patent”) discloses a particulate photocatalystdispersed in a coat-forming element. The photocatalyst preferablyconsists of titanium dioxide particles having a mean particle size of0.1 micron or less, where the titanium dioxide may be used in either theanatase or rutile form. The coat-forming element is capable of forming acoating of silicone resin when cured and is comprised of anorganopolysiloxane formed by partial hydrolysis of hydrolyzable silanesfollowed by polycondensation. In the '867 patent, the siliconecoat-forming element in itself is considerably hydrophobic, but uponexcitation of the dispersed photocatalyst, a high degree of wateraffinity, i.e., hydrophilicity, can be imparted to the coating.

Japanese Patent Application JP-8-164334A discloses a coatingfilm-forming composition comprising titanium oxide having an averageparticle diameter of 1 to 500 nanometers, a hydrolyzate of ahydrolyzable silicon compound, and a solvent. The hydrolyzable siliconcompound is an alkyl silicate condensate expressed by the formulaSi_(n)O_(n−1)(OR)_(2n+2) (where n is 2 to 6, and R is a C1-C4 alkylgroup). The hydrolyzate results from hydrolyzing the alkyl silicatecondensate at a hydrolysis percentage of 50 to 1500%. The hydrolyzateitself, however, is not believed to be hydrophilic.

U.S. Pat. Nos. 6,013,372 and 6,090,489 disclose photocatalytic coatingcompositions wherein particles of a photocatalyst are dispersed in afilm-forming element of uncured or partially cured silicone(organopolysiloxane) or a precursor thereof. The photocatalyst mayinclude particles of a metal oxide, such as the anatase and rutile formsof titanium dioxide. According to these patents, the coatingcompositions are applied on the surface of a substrate and thefilm-forming element is then subjected to curing. Then, uponphotoexcitation of the photocatalyst, the organic groups bonded to thesilicon atoms of the silicone molecules of the film-forming element aresubstituted with hydroxyl groups under the photocatalytic action of thephotocatalyst. The surface of the photocatalytic coating is thereby“superhydrophilified,” i.e., the surface is rendered highly hydrophilicto the degree that the contact angle with water becomes less than about10°. In these patents, however, the film-forming element in itself isconsiderably hydrophobic, i.e., the initial contact angle with water isgreater than 50°. As a result, the coating is initially hydrophobic, andit is only upon excitation of the dispersed photocatalyst thathydrophilicity is imparted to the coating.

U.S. Pat. No. 6,165,256 discloses compositions that can hydrophilify thesurface of a member to impart anti-fogging properties to the surface ofthe member. The compositions disclosed in this patent comprise (a)photocatalytic particles of a metallic oxide,(b) a precursor capable offorming a silicone resin film or a precursor capable of forming a silicafilm, and (c) a solvent, such as water, organic solvents, and mixturesthereof. The solvent is added in an amount such that the total contentof the photocatalytic particle and the solid matter of the precursor inthe composition is 0.01 to 5% by weight. As in the previous examples,however, hydrophilification of the coating formed from such acomposition takes place upon photoexcitation of the photocatalyst, whilethe film forming material in itself is not hydrophilic. Therefore, sucha coating is not believed to be hydrophilic prior to excitation of thephotocatalyst.

These prior art hydrophilic coatings that achieve their hydrophilicitythrough the action of a photocatalytic material that is dispersed in asilicon-containing binder suffer, however, from some drawbacks. Onenotable drawback is that these coatings do not exhibit hydrophilicityuntil photoexcitation of the photocatalyst. In addition, thesecompositions typically require a forced cure, i.e., they cannot beefficiently cured at room temperatures.

U.S. Pat. No. 6,303,229 (“the '229 patent”) discloses anothercomposition that may include a photocatalytic material. The coatingdisclosed in the '229 patent is formed from applying a coatingcomposition that contains a silicone resin, which acts as the binder andwhich is obtained by hydrolyzing and condensation-polymerizing certaintetra-functional alkoxysilanes. The coating compositions may alsoinclude colloidal silica. Evidently, the coated film formed from thecomposition disclosed in the '229 patent can be initially hydrophilic.This initial hydrophilicity, however, is believed to result from thepresence of colloidal silica in the composition rather than the siliconeresin itself. It is believed that the silicone resin disclosed in the'229 patent is not itself hydrophilic because the desired pH of theresin is 3.8 to 6, which indicates that Si—OR groups exist in the resinin an amount to prevent gellation and hydrophilicity. As a result, sucha coating suffers from some drawbacks. For example, such a coating thatincludes a photocatalytic material cannot be effectively applieddirectly over an organic base material without the inclusion of a primerlayer between the substrate and the coating composition containing thesilicon resin. Moreover, the inclusion of colloidal silica in thecoating composition will cause iridescence when the composition isapplied over an organic substrate at larger film thicknesses.

As a result, it would be advantageous to provide a composition thatincludes a photocatalytic material and a binder, wherein the coatingformed from such a composition can be hydrophilic prior to excitation ofthe photocatalyst and can be rendered super-hydrophilic upon excitationof the photocatalyst. It would also be advantageous to providecompositions of this type that have low haze, can be efficiently curedat ambient temperatures, and/or that maintain their hydrophilicity forlong periods of time when exposed to a dark state. Moreover, it would beadvantageous to embody such compositions in the form of a stableone-pack product.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart reflecting a Fourier Transform Infrared Spectroscopy(“FTIR”) analysis of a dry film formed from a hydrophilic bindermaterial in accordance with certain non-limiting embodiments of thepresent invention;

FIG. 2 is a schematic cross-sectional view in an enlarged scale ofcertain non-limiting embodiments of the present invention, and

FIG. 3 is a Field Emission Scanning Electron Microscope SecondaryElectron Micrograph (magnification 40,000×) depicting certainnon-limiting embodiments of the present invention.

FIG. 4 is a chart illustrating the results of the durability testingconducted as described in Example 2.

SUMMARY OF THE INVENTION

In one respect, the present invention is directed to liquidcompositions, such as coating compositions, comprising (a) aphotocatalytic material, and (b) a binder. The binder of thecompositions of the present invention is hydrophilic and comprises anessentially completely hydrolyzed organosilicate.

In another respect, the present invention is directed to methods ofmaking such liquid compositions, one-pack liquid compositions, methodsof coating a substrate with such liquid compositions, and substratescoated with the liquid compositions of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Forexample, and without limitation, this application refers to liquidcompositions that comprise “a photocatalytic material”. Such referencesto “a photocatalytic material” is meant to encompass compositionscomprising one photocatalytic material as well as compositions thatcomprise more than one photocatalytic material, such as compositionsthat comprise two different photocatalytic materials. In addition, inthis application, the use of “or” means “and/or” unless specificallystated otherwise, even though “and/or” may be explicitly used in certaininstances.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

The present invention is directed to liquid compositions, such ascoating compositions, comprising (a) a photocatalytic material, and (b)a binder. The binder of the compositions of the present invention ishydrophilic and comprises an essentially completely hydrolyzedorganosilicate.

The liquid compositions of the present invention comprise aphotocatalytic material. As used herein, the term “photocatalyticmaterial” refers to a material that is photoexcitable upon exposure to,and absorption of, radiation, such as ultraviolet or visible radiation.A photocatalytic material is a material that, when exposed to lighthaving higher energy than the energy gap between the conduction band andthe valence band of the crystal, causes excitation of electrons in thevalence band to produce a conduction electron thereby leaving a holebehind on the particular valence band. In certain embodiments of thepresent invention, the photocatalytic material comprises a metal oxide,such as zinc oxide, tin oxide, ferric oxide, dibismuth trioxide,tungsten trioxide, strontium titanate, titanium dioxide, or mixturesthereof.

In certain embodiments of the present invention, at least a portion ofthe photocatalytic material is present in the liquid composition in theform of particles having an average crystalline diameter of 1 to 100nanometers, such as 3 to 35 nanometers, or, in yet other embodiments, 7to 20 nanometers. In these embodiments, the average crystalline diameterof the particles can range between any combination of the recitedvalues, inclusive of the recited values. It will be understood by thoseskilled in the art that the average crystalline diameter of theparticles may be selected based upon the properties desired to beincorporated into the liquid composition. In some embodiments,substantially all of the photocatalytic material is present in the formof such particles. The average crystalline diameter of thephotocatalytic metallic oxide particles may be determined by scanningelectron microscope or transmission electro-microscope and the crystalphase of such particles may be determined by X-ray diffraction, as knownby those skilled in the art.

As mentioned above, certain materials may be photocatalytic uponexposure to, and absorption of, for example, ultraviolet (“UV”), and/orvisible radiation. In certain embodiments of the present invention, thephotocatalytic material comprises materials that are photoexcitable byone or more of these mechanisms. Examples of materials that may be usedin the present invention and which are photocatalytic upon exposure toUV radiation include, without limitation, tin oxide, zinc oxide, and thebrookite, anatase and rutile forms of titanium dioxide. Examples ofmaterials that may be used in the present invention and which arephotocatalytic upon, exposure to visible radiation include, withoutlimitation, the brookite form of titanium oxide, titanium dioxidechemically modified via flame pyrolysis of titanium metal, nitrogendoped titanium dioxide, and plasma treated titanium dioxide.

In certain embodiments of the present invention, the photocatalyticmaterial is provided in the form of a sol comprising particles ofphotocatalytic material dispersed in water, such as a titania sol. Suchsols are readily available in the marketplace. Examples of suchmaterials, which are suitable for use in the present invention, include,without limitation, S5-300A and S5-33B available from MilleniumChemicals, STS-01, STS-02, and STS-21 available from Ishihara SangyoCorporation, and NTB-1, NTB-13 and NTB-200 available from Showa DenkoCorporation.

In certain embodiments of the present invention, the photocatalyticmaterial is present in the form of a sol comprising brookite-typetitanium oxide particles or a mixture of brookite-type with anatase-typeand/or rutile-type titanium oxide particles dispersed in water. Suchsols can be prepared by hydrolysis of titanium tetrachloride undercertain conditions, such as is taught by U.S. Pat. No. 6,479,031, whichis incorporated herein by reference. Sols of this type which aresuitable for use in the present invention include, without limitation,NTB-1 and NTB-13 titania sols available from Showa Denko Corporation.

In certain embodiments of the present invention, the photocatalyticmaterial comprises chemically modified titanium dioxide. Examples ofsuch materials include titanium dioxide chemically modified by flamepyrolysis as described by Khan et al., Efficient Photochemical WaterSplitting by a Chemically Modified n-TiO ₂, Science Reprint, Volume 297,pp. 2243-2245-(2002), which is incorporated herein by reference,nitrogen-doped titanium oxide manufactured as described in U. S. PatentApplication Publication 2002/0169076A1 at, for example, paragraphs.[0152] to [0203], which is incorporated herein by reference, and/orplasma treated titanium dioxide as described in U.S. Pat. No. 6,306,343at col. 2, line 49 to col. 7, line 17, which is incorporated herein byreference.

In certain embodiments of the present invention, the amount of thephotocatalytic material that is present in the liquid composition rangesfrom 0.05 to 5 percent solids by weight, such as 0.1 .to 0.75 percentsolids by weight, with percent solids by weight being based on the totalsolution weight of the composition. In these embodiments, the amount ofphotocatalytic material that may be preset in the liquid composition canrange between any-combination of the recited values, inclusive of therecited values. It will be understood by those skilled in the art thatthe amount of photocatalytic material present in the liquid compositionis determined by the properties desired to be incorporated into thecomposition.

The liquid compositions of the present invention also comprise ahydrophilic binder. As used herein, the term “binder” refers to acontinuous material in which particles of the photocatalytic materialare dispersed. As used herein, the term “hydrophilic binder” means thatthe binder itself has an affinity for water. One way to assess thehydrophilicity of a material is to measure the contact angle of waterwith a dry film formed from the material. In certain embodiments of thepresent invention, the binder comprises a material that can form a dryfilm that exhibits a water contact angle of no more than 20°, or, inother embodiments, no more than 15°, or, in yet other embodiments, nomore than 10°.

As a result, in certain embodiments of the present invention, uponapplication of the liquid composition to a substrate and subsequentdrying, the resulting film exhibits an initial water contact angle of nomore than 20° or, in some embodiments, no more than 15°, or, in yetother embodiments, no more than 10°, prior to photoexcitation of thephotocatalytic material. The water contact angles reported herein are ameasure of the angle between a tangent to the drop shape at the contactpoint and the surface of the substrate as measured through the drop andmay be measured by the sessile drop method using a modified captivebubble indicator manufactured by Lord Manufacturing, Inc., equipped withGaertner Scientific goniometer optics. The surface to be measured isplaced in a horizontal position, facing upward, in front of a lightsource. A sessile drop of water is placed on top of the surface in frontof the light source so that the profile of the sessile drop can beviewed and the contact angle measured in degrees through the goniometertelescope which is equipped with circular protractor graduations.

In certain embodiments of the present invention, the liquid compositioncomprises a binder that exhibits anti-static properties, i.e., thebinder can form a dry film that has the ability to dissipateelectrostatic charges. As will be appreciated by those skilled in theart, one way to assess the anti-static capability of a material is tomeasure the surface resistivity of the material. In certain embodimentsof the present invention, the binder comprises a material that can forma dry film that exhibits a surface resistivity of from 7.5×10⁹ to1.5×10¹² ohms/cm², or, in other embodiments, no more than 1.0×10¹⁰ohms/cm². The surface resistivities reported herein can be determinedwith an ACL Statitide Model 800 Megohmeter using either (1) largeextension probes placed 5 millimeters apart at several locations on thesample, or (2) the meters onboard probes spaced 2¾ inches apart atseveral locations on the sample. As a result, the present invention isalso directed to liquid compositions having such anti-static properties.

The liquid compositions of the present invention comprise a binder thatcomprises an essentially completely hydrolyzed organosilicate. As usedherein, the term “organosilicate” refers to a compound containingorganic groups bonded to a silicon atom through an oxygen atom. Suitableorganosilicates include, without limitation, organoxysilanes containingfour organic groups bonded to a silicon atom through an oxygen atom andorganoxysiloxanes having a siloxane main chain ((Si—O)_(n)) constitutedby silicon atoms.

The organic groups bonded to the silicon atom through an oxygen atom inthe organosilicates are not limited and may include, for example,linear, branched or cyclic alkyl groups. Specific examples of theorganic groups that may be bonded to the silicon atom through an oxygenatom in the organosilicates include, without limitation, methyl, ethyl,n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, i-pentyl,neopentyl, hexyl, octyl or the like. Of these alkyl groups, C₁ to C₄alkyl groups are often used. Examples of other suitable organic groupsmay include aryl, xylyl, naphthyl or the like. The organosilicate maycontain two or more different kinds of organic groups.

Specific non-limiting examples of suitable organoxysilanes aretetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane,tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane,tetra-sec-butoxysilane, tetra-t-butoxysilane, tetraphenoxysilane, anddimethoxydiethoxysilane. These organosilicates may be used alone or incombination of any two or more thereof. Among these organosilicates,tetramethoxysilane and/or partially hydrolyzed condensates thereof showa high reactivity for hydrolysis and, therefore, can readily producesilanol groups.

Specific non-limiting examples of suitable organoxysiloxanes arecondensates of the above organoxysilanes. The condensation degree of theorganoxysiloxanes is not particularly restricted. In certainembodiments, the condensation degree lies within the range representedby the following formula:SiO_(x)(OR)_(y)wherein x is from 0 to 1.2, and y is from 1.4 to 4 with the proviso that(2x+y) is 4; and R is an organic group, such as C₁, to C₄ alkyl.

The factor or subscript x represents the condensation degree of thesiloxane. When the siloxane shows a molecular weight distribution, thefactor x means an average condensation degree. Compounds represented bythe above formula wherein x=0, are organoxysilanes as a monomer, andcompounds represented by the above formula wherein 0<x<2, are oligomerscorresponding to condensates obtained by partial hydrolysiscondensation. Also, compounds represented by the above formula whereinx=2, corresponds to SiO₂ (silica). In certain embodiments, thecondensation degree x of-the organosilicate used in the presentinvention is in the range of 0 to 1.2, such as 0 to 1.0. The siloxanemain chain may have a linear, branched or cyclic structure or a mixturethereof. The above formula: SiO_(x)(OR)_(y) may be determined by Si-NMRas described in U.S. Pat. No. 6,599,976 at col. 5, lines 10 to 41,incorporated herein by reference.

As mentioned earlier, the binder of the liquid compositions of thepresent invention comprises an organosilicate that is essentiallycompletely hydrolyzed. As used herein, the term “essentially completelyhydrolyzed organosilicate” refers to a material wherein the organoxygroups of the organosilicate are substantially replaced by silanolgroups to an extent that the material is rendered hydrophilic, i.e., thematerial can form a dry film that exhibits a water contact angle of nomore than 20°, or, in other embodiments, no more than 15°, or, in yetother embodiments, no more than 10°. This hydrolysis may produce anetwork polymer, as illustrated below:

where m and n are positive numbers and m is no more than n. In certainembodiments of the present invention, the essentially completelyhydrolyzed organosilicate is substantially free of —OR groups asdetermined by FTIR or other suitable analytical technique.

Referring now to FIG. 1, there is seen a chart reflecting an FTIRanalysis of a dry film formed from such a hydrophilic binder material.As is apparent, significant peaks are observed at the Si—OH bondwavenumber, which is 920-950, ad the Si—O—Si bond wavenumber, which is1050-1100. On the other hand, it is apparent that the film issubstantially free of —OR groups, where R represents C₁ to C₄ alkylgroups, as evidenced by the absence of any substantial peak at the Si—ORwavenumber, which is 2900-3000.

In certain embodiments, the essentially completely hydrolyzedorganosilicate included in the binder of the present invention is theproduct of the hydrolysis of an organosilicate with a large amount ofwater in the presence of an acid hydrolysis catalyst. The hydrolysis maybe conducted with water present in an amount considerably greater thanthe stoichiometric amount capable of hydrolyzing organoxy-groups of theorganosilicate. It is believed that the addition of such an excessiveamount of water allows silanol groups produced by hydrolysis of theorganosilicate to coexist with a large amount of water, therebypreventing the condensation reaction of the silanol groups.

The hydrolysis of the organosilicate may be conducted in the presence ofone or more acid hydrolysis catalysts. Specific examples of suitablecatalysts include, without limitation, inorganic acids, such ashydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, amongothers; organic acids, such as acetic acid, benzenesulfonic acid,toluenesulfonic acid, xylenesulfonic acid, ethylbenzenesulfonic acid,benzoic acid, phthalic acid, maleic acid, formic acid, citric acid, andoxalic acid, among others; alkali catalysts, such as sodium hydroxide,potassium hydroxide, calcium hydroxide, ammonia; and organic aminecompounds, or organometallic compounds or metal alkoxide compounds otherthan the organosilicates, e.g., organotin compounds, such as dibutyl tindilaurate, dibutyl tin dioctoate and dibutyl tin diacetate,organoaluminum compounds, such as aluminum tris(acetylacetonate ,aluminum monoacetylacetonate bis(ethylacetoacetate), aluminumtris(ethylacetoacetate) and ethylacetoacetate aluminum diisopropionate,organotitanium compounds, such as titanium tetrakis(acetylacetonate),titanium bis(butoxy), bis(acetylacetonate) and titaniumtetra-n-butoxide, and organozirconium compounds, such as zirconiumtetrakis(acetylacetonate), zirconium bis(butoxy)-bis(acetylacetonate),zirconium (isopropoxy)-bis(acetylacetonate) and zirconiumtetra-n-butoxide, and boron compounds, such as, boron tri-n-butoxide andboric acid; or the like.

In certain embodiments, the binder may also comprise, in addition towater, an organic solvent, such as alcohols, glycol derivatives,hydrocarbons, esters, ketones, ethers or the like. These solvents may beused alone or in the form of a mixture of any two or more thereof.

Specific examples of alcohols that may be used include, withoutlimitation, methanol, ethanol, n-propanol, isopropanol, n-butanol,isobutanol, acetylacetone alcohol or the like. Specific examples ofglycol derivatives that may be used include, without limitation,ethylene glycol, ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, propylene glycol, propylene glycol monomethyl ether,propylene glycol monoethyl ether, diethylene glycol monomethyl ether,diethylene glycol monoethyl ether, ethylene glycol monomethyl etheracetate, ethylene glycol monoethyl ether acetate, propylene glycolmonomethyl ether acetate, propylene glycol; monoethyl ether acetate orthe like. Specific examples of hydrocarbons that may. be used include,without limitation, benzene, toluene, xylene, kerosene, n-hexane or thelike. Specific examples of esters that may be used include, withoutlimitation, methyl acetate, ethyl acetate, propyl acetate, butylacetate, methyl acetoacetate, ethyl acetoacetate, butyl acetoacetate orthe like. Specific examples of the ketones that may be usedinclude-acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone or the like. Specific examples of ethers that may be usedinclude, without limitation, ethyl ether, butyl ether, methoxy ethanol,ethoxy ethanol, dioxane, furan, tetrahydrofuran or the like.

Binders suitable for use in the present invention and methods for theirproduction are described in U.S. Pat. No. 6,599,976 at col. 3, line 57to col. 10, line 58, incorporated herein by reference. Non-limitingexamples of commercially available materials that are essentiallycompletely hydrolyzed organosilicates, and which are suitable for use inthe binder in the compositions of the present invention are MSH-200,MSH-400, and MSH-500, silicates available from Mitsubishi ChemicalCorporation, Tokyo, Japan and Shinsui Flow MS-1200, available fromDainippon Shikizai, Tokyo, Japan.

In certain embodiments, the binder is prepared in a multi-stage processwherein, in a first stage, an organoxysilane, such as any of thosementioned earlier, is reacted with water in the presence of an acidhydrolysis catalyst, such as any of those mentioned earlier, wherein thewater is present in an amount that is less than the stoichiometricamount capable of hydrolyzing the organoxy groups of the organoxysilane.In certain embodiments, the acid hydrolysis catalyst comprises anorganic acid. In certain embodiments, the water is present during thefirst stage in a stoichiometric amount capable of hydrolyzing 50 percentof the organoxy groups of the organoxysilane. The result of the firststage is a partial hydrolysis polycondensation reaction product.

In certain embodiments, the first stage of the multi-stage binderpreparation process is conducted at conditions that limit the degree ofcondensation of Si—OH groups formed as a result of the hydrolysisreaction. Such conditions can include, for example, controlling thereaction exotherm by, for example, external cooling, controlling therate of addition of the acid catalyst, and/or conducting the first stagehydrolysis in the substantial absence (or complete absence) of anyorganic cosolvent.

In a second stage, the partial hydrolysis polycondensation reactionproduct is then contacted with a large amount of water, often in theabsence of an acid hydrolysis catalyst. The amount of water used in thesecond stage is considerably greater (by “considerably greater” it ismeant that the resulting solution contains no more than 2% solids) thanthe stoichiometric amount capable of hydrolyzing organoxy groups of theorganoxysilane.

In yet other embodiments, the binder is prepared by starting with atetraalkoxysilane oligomer, such as those commercially available fromMitsubishi Chemical Corp. under the tradenames MKC Silicate MS-51, MKCSilicate MS-56 and MKC Silicate MS-60 (all trademarks; products ofMitsubishi Chemical, Corp.). Such an oligomer is reacted with water inthe presence of an organic acid hydrolysis catalyst (such as, forexample, acetic acid) and/or an organic solvent, wherein the water ispresent in an amount that is considerably greater than thestoichiometric amount capable of hydrolyzing organoxy groups of thetetralkoxysilane.

As a result, the present invention is also directed to methods formaking hydrophilic compositions comprising an essentially completelyhydrolyzed organosilicate. The Examples herein describe exemplaryconditions for such methods.

In certain embodiments of the present invention, the amount oforganosilicate that is present in the liquid composition ranges from 0.1to 2 percent by weight calculated as SiO₂ in the organosilicate, such as0.2 to 0.9 percent by weight based on the total weight of thecomposition. In these embodiments, the amount of the organosilicate thatmay be present in the liquid composition can range between anycombination of the recited values, inclusive of the recited values. Itwill be understood by those skilled in the art that the amount of theorganosilicate present in the liquid composition is determined by theproperties desired to be incorporated into the composition.

In certain embodiments of the present invention, the photocatalyticmaterial and the organosilicate are present in the liquid composition ata ratio of 0.05:0.95 to 5:0.3 by weight, or, in other embodiments0.10:0.90 to 3.0:0.5 by weight, or, in yet other embodiments, at least0.3:0.5 by weight, or 0.2:0.6 by weight. In these embodiments, the ratioof the photocatalytic material to the organosilicate can range betweenany combination of the recited values, inclusive of the recited values.It will be understood by those skilled in the art that the ratio ofphotocatalytic material and organosilicate in the liquid composition isdetermined by the properties desired to be incorporated into thecomposition, such as the refractive index desired for the compositionwhich may be determined with reference to the substrate upon which thecomposition is to be applied.

In certain embodiments, the liquid compositions of the present inventioncan further include inorganic particles, for example, silica, alumina,including treated alumina (e.g. silica-treated alumina known as alphaaluminum oxide), silicon carbide, diamond dust, cubic boron-nitride, andboron carbide. Such inorganic particles may, for example, besubstantially colorless, such as silica, for example, colloidal silica.Such materials may provide enhanced mar and scratch resistance. Suchparticles can have an average particle size ranging from sub-micron size(e.g. nanosized particles) up to 10 microns depending upon the end useapplication of the composition and the desired effect.

In certain embodiments, the particles comprise inorganic particles thathave an average particle size ranging from 1 to 10 microns, or from 1 to5 microns prior to incorporation into the liquid composition. In otherembodiments, the particles may have an average particle size rangingfrom 1 to less than 1000 nanometers, such as 1 to 100 nanometers, or, incertain embodiments, 5 to 50 nanometers, prior to incorporation into theliquid composition. In some embodiments, the inorganic particles have anaverage particle size ranging from 5 to 50, or 5 to 25 nanometers priorto incorporation into the liquid composition. The particle size mayrange between any combination of these values inclusive of the recitedvalues.

In certain embodiments of the present invention, the particles can bepresent in the liquid composition in an amount ranging from up to 5.0percent by weight, or from 0.1 to 1.0 weight percent; or from 0.1 to 0.5weight percent based on total weight of the composition. The amount ofparticles present in the liquid composition can range between anycombination of these. values. inclusive of the recited values.

In certain embodiments of the present invention the liquid compositionalso comprises an antimicrobial enhancing material, such as, forexample, metals; such as silver, copper, gold, zinc, a compound thereof,or a mixture thereof; quaternary ammonium compounds, such asbenzalkonium chlorides, dialkyldimethyl-ammonium chlorides,cetyltrimethy-ammonium bromide, cetylpyridinium chloride, and3-(trimethoxysilyl)-propyldimethyl-octadecyl-ammonium chloride;phenolics, such as 2-benzyl-4-chlorophenol, o-phenylphenol, sodiumo-phenylphenate, pentachlorophenol,2(2′,4′-dichlorophenoxy)-5-chlorophenol, and 4-chloro-3-methylphenol;halogen compounds, such as trichloroisocyanurate, sodiumdichloroisocyanurate, potassium dichloroisocyanurate,monotrichloroisocyanurate, potassium dichloro-isocyanurate, 1:4dichlorodimethylhydantoin, bromochlorodimethylhydantoin,2,2′-dibromo-3-nitrilopropionamide, bis(1,4-bromoacetoxy)-2-butene,1,2-dibromo-2,4-dicyanobutane, 2-bromo-2-nitropropane-1,3-diol, andbenzyl bromoacetate; organometallics, such as10,10′-oxybisphenoxiarsine, tributyltin oxide, tributyltin fluoride,copper 8-quinolinolate, copper naphthenate, chromated copper arsenate,ammoniacal copper arsenate, and cuprous oxide; organosulfur compounds,such as methylenebisthiocyanate (MBT), vinylenebisthiocyanate,chloroethylenebisthiio-cyanate, sodium dimethyldithiocarbamate, disodiumethylenebisdithiocarbamate, zinc dimethyldithiocarbamate, andbis(trichloromethyl) sulfone; heterocyclics, such astetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione (DMTT), sodiumpyridinethione, zinc pyridinethione, 1,2-benzisothiazoline-3-one,2-(n-octyl)-4-isothiazolin-3-one, 2-(4-thiazolyl)benzimidazole,N-(trichloromethylthio)-4-cyclohexene-1,2-dicarboximide,N-(trichloromethylthio)-phthalimide, and5-chloro-2-methyl-4-isothiazolin-3-one 2-methyl-4-isothiazolin-3-one;and nitrogen compounds, such as N-cocotrimethylenediamine,N-[α-(1-nitroethyl)benzyl]-ethylenediamine,2-(hydroxymethyl)amino-ethanol, 2-(hydroxymethyl)amino-2-methylpropanol,2-hydroxymethyl-2-nitro-1,3-propanediol,hexahydro-1,3,5-tris-(2-hydroxyethyl)-s-triazine,hexahydro-1,3,5-triethyl-s-triazine,4-(2-nitrobutyl)morpholine+4,4′-(2-ethyl-2-nitro-trimethylene)-dimorpholine,glutaraldehyde, 1,3-dimethylol-5,5-dimethyl-hydantoin, andimidazolidinyl urea, and mixtures thereof.

The liquid compositions of the present invention may, for example,contain a quantity of antimicrobial agent sufficient to exhibit anefficacy against microbes and particularly various species of fungi.More specifically, embodiments of the present invention may contain aquantity of antimicrobial agent sufficient to inhibit microbial growthon a substrate tested in accordance with MTCC (American Association ofChemists & Colorists) Test Method 30, Part III. Those skilled in the artare familiar with this test method and its parameters.

In certain embodiments of the present invention, the amount ofantibacterial enhancing material that is present in the liquidcomposition ranges from 0.01 to 1.0 percent by weight, such as 0.1 to1.0 percent by weight, or, in other embodiments, 0.1 to 0.5 percent byweight based on the total weight of the composition. In theseembodiments, the amount of the antibacterial enhancing material that maybe present in the liquid composition can range between any combinationof the recited values, inclusive of the recited values. It will beunderstood by those skilled in the art that the amount of theantibacterial enhancing material present in the liquid composition isdetermined by the properties desired to be incorporated into thecomposition.

In certain embodiments, the liquid compositions of the present inventionmay comprise an optical activity enhancer, such as platinum, gold,palladium, iron, nickel, or soluble salts thereof. The addition of thesematerials to compositions comprising a photocatalytic material is knownto enhance the redox activity of the photocatalyst, promoting,decomposition of contaminants adhering to the coating surface. Incertain embodiments of the present invention, the amount of opticalactivity enhancer present in the liquid composition ranges from 0.01 to1.0 percent by weight, such as 0.1 to 1.0 percent by weight, or, inother embodiments, 0.1 to 0.5 percent by weight based. on the totalweight of the composition. In these embodiments, the amount of opticalactivity enhancer that may be, present in the liquid composition canrange between any combination of the recited values, inclusive of therecited values. It will be understood by those skilled in the art thatthe amount of the optical activity enhancer present in the liquidcomposition is determined by the properties desired to be incorporatedinto the composition.

In certain embodiments, the liquid compositions of the present inventionmay comprise a coupling agent, which may, for example, improve theadhesion of the compositions of the present invention to paintedsubstrates. Examples of coupling agents suitable for use in the liquidcompositions of the present invention include, without limitation, thematerials described in U.S. Pat. No. 6,165,256 at col. 8, line 27 tocol. 9, line 8, incorporated herein by reference.

In certain embodiments of the present invention, the amount of couplingagent that is present in the liquid composition ranges from 0.01 to 1percent by weight, such as, 0.1to 0.5 percent by weight based on thetotal weight of the composition. In these embodiments, the amount ofcoupling agent that may be present in the liquid composition can rangebetween any combination of the recited values, inclusive of the recitedvalues. It will be understood by those skilled in the art that theamount of coupling agent present in the liquid composition is determinedby the properties desired to be incorporated into the composition.

In certain embodiments, the liquid compositions of the present inventionmay comprise a surface active agent, which may, for example, aid inimproving the wetting properties of the composition, particularly whenthe composition is applied over a coated substrate, such as a substratecoated with an organic coating. Examples of surface active agentssuitable for use in the present invention include, without limitation,the materials identified in U.S. Pat. No. 6,610,777 at col. 37, line 22to col. 38, line 60 and U.S. Pat. No. 6,657,001 at col. 38, line 46 tocol. 40, line 39, which are both incorporated herein by, reference.

In certain embodiments of the present invention, the amount ofsurfactant that is present in the liquid composition ranges from 0.01 to3 percent by weight, such as 0.01 to 2 percent by weight, or, in otherembodiments, 0.1 to 1 percent by weight based on the total weight ofsolids in the composition. In these embodiments, the amount ofsurfactant that may be present in the liquid composition can rangebetween any combination of the recited values, inclusive of the recitedvalues. It will be understood by those. skilled in the art that theamount of surfactant present in the liquid composition is determined bythe properties desired to be incorporated into the composition.

In certain embodiments, the liquid compositions of the present inventionmay comprise a cleaning composition. Suitable cleaning compositionsincludes those materials that comprise a surfactant, a solvent system,water, and a pH adjusting agent, such as acetic acid or ammonia. Asuitable cleaning composition is disclosed in U.S. Pat. No. 3,463,735,which discloses a cleaning composition comprising a solvent systemcomprising a low boiling solvent, such as isopropanol, and a moderatelyhigh boiling solvent, such as a C₁ to C₄ alkylene glycol alkyl etherhaving a total of 3 to 8 carbon atoms. Suitable commercially availablecleaning compositions include WINDEX®, commercially available from SCJohnson and Son, Inc. The inventors have discovered that the inclusionof a cleaning composition to certain embodiments of the presentinvention can improve the wetting properties of the present compositionswhen applied to painted surfaces, such as aluminum-clad window sashes,aluminum siding, and the like. As a result, in certain embodiments, thepainted surface need not be cleaned prior to application of the liquidcompositions of the present invention.

Certain embodiments of the present invention, therefore, are directed toliquid compositions comprising (a) a cleaning composition, and (b) anessentially completely hydrolyzed organosilicate. Such compositions mayalso include a photocatalytic material, as described earlier.

In certain embodiments, the cleaning composition is present in theliquid compositions of the present invention in an amount of at least 10weight percent, such as at least 20 weight percent, or, in some cases atleast 25 weight percent, with weight percent being based on the totalweight of the liquid composition.

If desired, the coating composition can comprise other optional coatingmaterials well known to those skilled in the coatings art.

The present invention is also directed to methods of making liquidcompositions. According to certain methods of the present invention, aliquid composition is prepared by (a) providing a hydrophilic materialcomprising an essentially completely hydrolyzed organosilicate, whereinthe pH of the hydrophilic material is no more than 3.5; (b) providing asol or paste comprising a photocatalytic material dispersed in adiluent, wherein the pH-of the sol is no more than 3.5; and (c) mixingthe hydrophilic material provided in (a) with the sol or paste providedin (b) to, disperse the photocatalytic material in the hydrophilicmaterial. It has been found that liquid compositions made by this methodcan be stable for over 12 months with little or no agglomeration orprecipitation. The pH values reported herein can be determined using anACCUMET pH meter commercially available from Fisher Scientific..

Certain methods of the present invention comprise the step of providinga hydrophilic material comprising an essentially completely hydrolyzedorganosilicate, wherein the pH of the hydrophilic material is no morethan 3.5 or, in some embodiments, from 1.3 to 3.5 or, in yet otherembodiments 3.0 to 3:5. In certain embodiments of the methods of thepresent invention, such a hydrophilic material is obtained by firstproviding a material comprising an essentially completely hydrolyzedorganosilicate wherein the pH of the material is greater than thedesired pH and then adding, acid to the material until the pH of thematerial is no more than 3.5 or, in some embodiments from 1.3 to 3.5 or,in yet other embodiments, 3.0 to 3.5. For example, as mentioned earlier,the hydrophilic material may comprise the MSH-200 and/or MS-1200silicates, both of which are typically provided by the supplier at a pHof 3.5 to 4.5.

In certain embodiments of the methods of the present invention, thehydrophilic material may be diluted with a diluent, such as water or anorganic solvent, before the addition of acid to, for example, reduce thesolids content of the hydrophilic material, thereby allowing for theformation of thinner films, as described below.

Acids that may be added to the hydrophilic material to adjust the pHthereof include both inorganic and organic acids. Suitable inorganicacids include, without limitation, hydrochloric acid, sulfuric acid,nitric acid and phosphoric acid, among others. Suitable organic acidsinclude acetic acid, dichloroacetic acid, trifluoroacetic acid,benzenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid,ethylbenzenesulfonic acid, benzoic acid, Phthalic acid, maleic acid,formic acid and oxalic acid, among others.

Certain methods of the present invention comprise the step of providinga sol or paste comprising a photocatalytic material dispersed in adiluent, wherein the pH of the sol or paste is no more than 3.5 or, insome embodiments, from 1.3 to 3.5 or, in yet other embodiments 3.0 to3.5. In certain embodiments, the pH of the sol or paste is substantiallythe same as that of the hydrophilic material provided in step (a) of theinvention. In certain embodiments of the methods of the presentinvention, such a sol or paste is obtained by first providing such a solor paste wherein the pH thereof is greater than the desired pH and thenadding acid to the sol or paste until the pH of the sol or paste is nomore than 3.5 or, in some embodiments from 1.3 to 3.5 or, in yet otherembodiments, 3.0 to 3.5. For example, as mentioned earlier, thephotocatalytic material used in the compositions of the presentinvention may comprise a sol of titanium oxide available from ShowaDenko Corporation under the names NTB-1 and NTB-13, wherein the socomprises brookite-type titanium oxide particles or a mixture ofbrookite-type with anatase-type and/or rutile-type titanium oxideparticles dispersed in water. NTB-1 and NTB-13 are typically provided bythe supplier at a pH of 2 to. 4.

Acids that may be added to the sol or paste comprising thephotocatalytic material to adjust the pH, thereof include both theinorganic and organic acids described earlier, among others. In certainembodiments of the present invention, the acid that is added to the solor paste comprising the photocatalytic material is the same acid that isadded to the hydrophilic material provided in step (a) of the invention.

The methods of the present invention comprise the step of mixing thehydrophilic material, provided in step (a) with the sol or pasteprovided in step (b) to disperse the photocatalytic material in thehydrophilic material. The mixing step is not particularly limited andmay be accomplished by any conventional mixing technique known to thoseof skill in the art, so long as the mixing results in a dispersion ofthe photocatalytic material in the hydrophilic material. As a result,the present invention is also directed to the liquid compositionsdescribed above, wherein the pH of the composition is no more than 3,such as 1.3 to 3.5, or, in some embodiments, 3.0 to 3.5.

According to certain other methods of the present invention, a liquidcomposition is prepared by (a) providing a hydrophilic materialcomprising an essentially completely hydrolyzed organosilicate, whereinthe pH of the hydrophilic material is from 7.0 to 8.5; (b) providing asol or paste comprising a photocatalytic material dispersed in adiluent, wherein the pH of the sol or paste is from 7.0 to 8.5; and (c)mixing the hydrophilic material provided in (a) with the sol or pasteprovided in (b) to disperse the photocatalytic material in thehydrophilic material.

These methods of the present invention comprise the step of providing ahydrophilic material comprising an essentially completely hydrolyzedorganosilicate, wherein the pH of the hydrophilic material is from 7.0to 8.5, such as 7.0 to 8.0 or, in some embodiments, 7.5 to 8.0. Incertain embodiments of these methods of the present invention, such ahydrophilic material is obtained by first providing a materialcomprising an essentially completely hydrolyzed organosilicate whereinthe pH of the material is less than the desired pH and then adding abase compound to the material until the pH of the material is from 7.0to 8.5, such as 7.0 to 8.0 or, in some cases, 7.5 to 8.0.

In certain embodiments of these methods of the present invention, thehydrophilic material may be diluted with water prior to addition of thea base compound as described earlier.

Materials that may be added to the hydrophilic material to adjust the pHthereof include both organic bases and inorganic bases. Specificexamples of bases which may be used to raise the pH of the hydrophilicmaterial include, without limitation, alkali metal hydroxides, such assodium hydroxide, potassium hydroxide and lithium hydroxide; ammoniumhydroxide; quaternary ammonium hydroxides, such as tetraethyl ammoniumhydroxide and tetraethanol ammonium hydroxide; amines such as,triethylamine and 3-(diethylamino)-propan-1-ol; tertiary sulfoniumhydroxides, such as trimethyl sulfonium hydroxide and triethyl sulfoniumhydroxide; quaternary phosphonium hydroxides, such as tetramethylphosphonium hydroxide and tetraethyl phosphonium hydroxide;organosilanolates, such as tripotassium γ-aminopropylsilantriolate,tripotassium N-(β-aminoethyl)-γ-aminopropylsilantriolate, dipotassiumdimethylsilandiolate, potassium trimethylsilanolate,bis-tetramethylammonium dimethylsilandiolate, bis-tetraethylammoniumdimethylsilandiolate, and tetraethylammonium trimethylsilanolate; sodiumacetate; sodium silicate; ammonium bicarbonate; and mixtures thereof.

These methods of the present invention comprise the step of providing asol or paste comprising a photocatalytic material dispersed in adiluent, wherein the pH of the sol or paste is from 7.0 to 8.5, such as7.0 to 8.0.. or, in some embodiments, from 7.5 to 8.0. In certainembodiments, the pH of the sol or paste is substantially the same asthat of the hydrophilic material (a). In certain embodiments of thesemethods of the present invention, such a sol or paste is obtained byfirst providing such a sol or paste wherein the pH thereof is less thanthe desired pH and then adding a base to the sol or paste until, the pHthereof is from 7.0 to 8.5, such as 7.0 to 8.0 or, in some embodimentsfrom 7.5 to 8.0.

Bases that may be added to the sol or paste comprising thephotocatalytic material to adjust the pH thereof include the inorganicand organic bases described earlier, among others. In certainembodiments of the present invention, the base that is added to the solor paste comprising the photocatalytic material is the same as thatadded to the hydrophilic material provided in step (a) of the invention.

These methods of the present invention further comprise the step ofmixing the hydrophilic material provided in step (a) with the sol orpaste provided in step (b) to disperse the photocatalytic material inthe hydrophilic material. The mixing step is not particularly limitedand may be accomplished by any conventional mixing technique known tothose of skill in the art, so long as the mixing results in a dispersionof the photocatalytic material in the hydrophilic material. It has beenfound that liquid compositions made by this method are stable for 24 to72 hours with only a small amount of precipitation. As a result, thepresent invention is also directed to the liquid compositions describedabove, wherein the pH of the composition is from 7.0 to 8.5, such as7.0to 8.0, or, in some cases, 7.5 to 8.0.

Referring now to FIGS. 2 and 3 there is seen (i) a schematiccross-sectional view in an enlarged scale of certain non limitingembodiments of the present invention, and (ii) a micrograph illustratingan embodiment of the present invention, respectively. As is apparentfrom FIGS. 2 and 3, in certain embodiments of the present invention,coatings are formed wherein the photocatalytic material is dispersedthroughout the hydrophilic binder. In these embodiments, the coatingscomprise a photocatalytic material in the form of nano-sizedphotocatalytic particles 10 (in these particular examples, the particleshave an average crystalline diameter no more than 20 nanometers), whichare relatively uniformly dispersed throughout the hydrophilic binder 20.In particular, it is apparent, particular from FIG. 3, that theparticles 10 are non-agglomerated, i.e., all or nearly all of theparticles are encapsulated by, and separated by, the, binder rather thanbeing combined to each other. While not being limited by any theory, itis believed that, by controlling the pH of the hydrophilic material andthe sol or paste of photocatalytic material, prior to their combination,the, photocatalytic particles can be well dispersed in the hydrophilicmaterial, such that agglomeration is prevented, which results in aliquid composition of low turbidity. Thus, the present invention is alsodirected to liquid compositions having low turbidity as described below.

Because the photocatalytic particles are prevented from agglomerating incertain compositions of the present invention, the compositions can beapplied directly over an organic film while resulting in little, if any,direct contact between the photocatalytic material, such as titaniumdioxide particles, and the organic film. As a result, one advantage ofembodiments of the present invention is that the liquid compositions canbe applied directly to an organic film without the need for any barrierlayer between the compositions of the present invention and the organicfilm. As will be appreciated by those skilled in the art, the —OH freeradical that is generated by the photocatalytic action of aphotocatalytic material, such as titanium dioxide, will otherwisedegrade an organic film that is in direct contact with thephotocatalytic material.

One advantage of the liquid compositions of the present invention and/orthe methods of producing liquid compositions of the present invention isthat they may result in stable one-package liquid compositions.Therefore, the present invention is also directed to one-pack liquidcompositions. As used herein, the term “one-pack liquid composition”.refers to a liquid composition wherein the components comprising theliquid composition are stored together in a single container.

The one-pack liquid compositions of the present invention comprise atleast two components, including the previously discussed photocatalyticmaterials and hydrophilic binders. In addition, the one-pack liquidcompositions of the present invention have a shelf-life of at least 3months. As used herein, the term “shelf-life” refers to the amount oftime between when the components are combined in a single container andthe occurrence of precipitation or agglomeration to an extent that theturbidity of the liquid composition increases such that the compositioncan no longer form a low haze film. According to certain embodiments ofthe present invention, the stable one-pack liquid compositions have ashelf-life of at least 3 months or, in certain other embodiments, atleast 6 months, or, in other embodiments, at least 12 months.

In certain embodiments, the liquid compositions of the present inventionhave a turbidity of no more than 600 NTU; or, in some cases, no morethan 400 NTU: (Nephelometric Turbidity Units) after 3 months, 6 months,or; in some cases, 12 months. The turbidity values reported herein canbe determined by a Turbidimeter, Model DRT-100D, manufactured by ShabanManufacturing Inc, H. F. Instruments Division using a sample cuvette of28 mm diameter by 91 mm in length with a flat bottom. Moreover, coatingfilms deposited from compositions of the present invention, in certainembodiments, have low haze. As used herein, “low haze” means that thefilm has a haze of no more than 0.3%. The haze values reported hereincan be determined with a haze meter, such as a Hazegard® Model No.XL-211, available from Pacific Scientific Company, Silver Spring, Md.

The liquid compositions of the present invention may also be present inthe form of a multi-pack product. Therefore, the present invention isalso directed to multi-pack products comprising a first componentcomprising the previously discussed photocatalytic materials and asecond component. comprising the previously discussed hydrophilicbinder. As used herein, the term “multi-pack product” refers to acoating product comprising more than one component wherein thecomponents are combined just prior to application to a substrate.

The present invention is also directed to methods of coating a substratewith a liquid composition. These methods of the present inventioncomprise the steps of (a) applying to a substrate a liquid composition,and (b) curing the composition. The substrate may be cleaned with, forexample, an alcohol/water mixture, and dried prior to step (a). Theliquid compositions used in these methods of the present inventioncomprise the previously discussed photocatalytic materials andhydrophilic binders.

In these methods of the present invention, the liquid composition may beapplied to the substrate by any desired technique, such as, for example,spray coating, roll coating, dipping, spin coating, flow coatingbrushing, and wiping. The liquid compositions of the present inventionmay be applied to polymeric, ceramic, concrete, cement, glass, wood,paper or metal substrates, composite materials thereof, or othermaterials, including painted substrates. As suggested previously, theliquid compositions of the present invention may be effectively applieddirectly on organic films that may exist on a surface of suchsubstrates. Multiple layers of the compositions of the present inventioncan be applied if desired. Substrates that are reactive with silanolgroups may “anchor” the compositions of the present invention therebyproviding improved adhesion.

Specific examples of articles upon which the liquid compositions of thepresent invention may be applied include, without limitation, windows;windshields on automobiles, aircraft, watercraft and the like; indoorand outdoor mirrors; lenses, eyeglasses or other optical instruments;protective sports goggles; masks; helmet shields; glass slides offrozen, food display containers glass covers; buildings walls; buildingroofs; exterior tiles on buildings; building stone; painted steelplates; aluminum panels; window sashes; screen doors; gate doors; sunparlors; handrails; greenhouses; traffic signs; transparent soundproofwalls; signboards; billboards; guardrails; road reflectors; decorativepanels; solar cells; painted surfaces on automobiles watercraft,aircraft, and the like; painted surfaces; on lamps, fixtures, and otherarticles; air handling systems and purifiers; kitchen and bathroominterior furnishings and appliances; ceramic tiles; air filtrationunits; store showcases; computer displays; air conditioner heatexchangers, high-voltage cables; exterior and interior members ofbuildings; window panes; dinnerware; walls in living spaces, bathrooms,kitchens, hospital rooms, factory spaces, office spaces, and the likesanitary ware, such as basins, bathtubs, closet bowls, urinals, sinks,and the like; and electronic equipment, such as computer displays.

The liquid compositions of the present invention may be applied to asubstrate by, for example, impregnating a paper, cloth, or non-wovenfabric with a liquid composition of the present invention. Theimpregnated material, may be stored in a container and removed whenneeded to wipe-coat a surface of a substrate. Alternatively, a paper,cloth, or non-woven fabric could be impregnated with a liquidcomposition of the present invention at the time of use.

In the methods of coating a substrate of the present invention, theliquid composition is cured, i.e., dried, after it is applied to thesubstrate. Though not being bound by any theory, it is believed that,upon cure, some of the silanol groups of the essentially completelyhydrolyzed binder are condensed so that Si—O—Ti bonds are formed withinthe dried film formed from the liquid composition.

It is believed that the presence of these groups enhances the durabilityof coatings formed from the compositions of the present invention, asdescribed in more detail below.

The liquid compositions may be self-curing, such that the compositionsmay cure without the aid of any cure catalyst. Moreover, the liquidcompositions of the present invention may, for example, be cured atambient temperatures. In other words, curing of the liquid compositionsof the present invention maybe accomplished by allowing the compositionto stand in air, i.e., air drying. According to certain embodiments ofthe present invention, the liquid composition is cured by exposing it toair for 2 to 3 hours at 25° C. to achieve superhydrophilicity and 16hours to achieve long-term durability. The liquid compositions of thepresent invention may also be cured by heat drying. For, example,according to certain embodiments of the present invention, the liquidcomposition is cured by exposing it to air for 3 to 5 minutes and thenforce drying it at 80° C. to 100° C. for at least 3 seconds.

One of the features of certain embodiments of the present invention isthat the liquid composition can have a very low solids content,approximately 1 percent by weight total solids based on the total weightof the composition. Consequently, the liquid composition can be appliedto a substrate at extremely small film thicknesses. In particular,according to certain embodiments of the present invention, thecomposition is applied to a substrate in the form of a thin film thathas a dry film thickness of no more than 200 nanometers (0.2micrometers) or, in some embodiments, 10 to 100 nanometers. (0.01.to 0.1micrometers), in yet other embodiments of the present invention, 20 to60 nanometers (0.02 to 0.06 micrometers).Application of the compositionsof the present invention at such low film thickness can be particularadvantageous in providing an optical thin film without necessarilymatching the refractive index of the coating to that of the substrate.

As mentioned previously, coatings formed from the liquid compositions ofthe present invention are initially hydrophilic, that is, uponapplication, and prior to excitation of the photocatalyst, the coatingexhibits an affinity to water. This initial hydrophilicity results fromthe hydrophilicity of the binder and can be illustrated by an initialwater contact angle of no more than 20° or, in some embodiments, no morethan 15°, or, in yet other embodiments, no more than 10°. Uponexcitation of the photocatalytic material, however, the coatings formedfrom the liquid compositions of the present invention can be rendered“super-hydrophilic,” that is, following excitation of the photocatalyst,such coatings can exhibit a water contact angle of less than 5°, even aslittle as 0°.

The means that may be used for exciting the photocatalyst depends on thephotocatalytic material used in the liquid compositions of the presentinvention. For example, materials that are photoexcited upon exposure tovisible light, such as the brookite form of titanium dioxide, as well asnitrogen or carbon doped titanium dioxide, may be exposed to any visiblelight source including any radiation of a wavelength of at least 400nanometers. On the other hand, the anatase and rutile forms of titaniumdioxide, tin oxide, and zinc oxide can be photoexcited by exposure UVradiation of a wavelength of less than 387nanometers, 413 nanometers,344 nanometers, and 387 nanometers, respectively. Suitable UV radiationsources for photoexciting such photocatalysts include, withoutlimitation, a UV lamp, such as that sold under the tradename UVA-340 bythe Q-Panel Company of Cleveland, Ohio, having an intensity of 28 wattsper square meter (W/m²) at the coating surface.

In certain embodiments, coatings made from the liquid compositions ofthe present invention exhibit a photoactivity of at least 0.5cm⁻¹ min⁻¹such as at least 1.0 cm⁻¹ min⁻¹. Photoactivity can be evaluated asdescribed in U.S. Pat. No. 6,027,766 at col. 11, line 1 to col. 12, line55, which is incorporated herein by reference.

In certain embodiments, coatings formed from the liquid compositions ofthe present invention can be rendered superhydrophilic upon exposure tosunlight for a period of 1 to 2 hours. Alternatively, coatings formedfrom the liquid compositions of the present invention maybe renderedsuperhydrophilic upon exposure to UV radiation of an intensity of 28W/m² for 1 hour.

As discussed previously, coatings formed from the liquid compositions ofthe present invention can exhibit very favorable hydrophilic,anti-static and/or anti-bacterial properties, among others. Because theyare hydrophilic, and rendered superhydrophilic upon photoexcitation ofthe photocatalytic material, coatings made from the compositions of thepresent invention may exhibit advantageous self-cleaning, anti-fouling,and/or anti-fogging properties. The present invention, therefore, isalso directed to methods of rendering a surface of a substrateself-cleaning, anti-fouling, and/or anti-fogging.

Another feature of coatings made from the compositions of the presentinvention is that they may be particularly durable. The surprisingdurability of coatings made from the compositions of the presentinvention can be measured in terms of the ability of the film surface tomaintain a contact angle over time under accelerated weather conditions.The lower the degree of contact angle that can be maintained by thesample tested over time or number of wiping cycles, the more durable thefilm. Simulating weathering of the film can be obtained via weatheringchambers, which include the Cleveland Condensing Cabinet (CCC) and QUVTester (products of The Q-Panel Company, Cleveland, Ohio).

In certain embodiments, the photocatalytic material is present in theliquid compositions of the present invention in an amount sufficient toproduce a coating that maintains a contact angle of less than 10degrees, such as less than 5 degrees and/or a phtoactivity of 3 cm⁻¹min⁻¹ after exposure to a CCC chamber for 4000 hours, where the CCCchamber is operated at a vapor temperature of 140° F. (60° C.) in anindoor ambient environment which results in constant water condensationon the test surface. Indeed, as illustrated by the Examples herein, itwas discovered that the inclusion of a photocatalytic material incertain embodiments of the compositions of the present inventionproduced coatings exhibiting dramatically improved durability ascompared to compositions containing a hydrophilic binder of the typedescribed herein but no photocatalytic material. As illustrated by FIG.4, in certain embodiments of the present invention, the photocatalyticmaterial can be included in the composition in an amount sufficient toyield a coating that maintains its initial water contact angle (i.e.,the water contact angle is within 4degrees of the initial water contactangle, wherein “initial water contact angle” refers to the water contactangle observed after exposure to UV light for 2 hours as described inthe Examples but before exposure to the CCC chamber) even after exposureof the, coating to a CCC chamber for 4000 hours as described above,whereas the absence of a photocatalytic material yielded a coating thatcould not maintain its initial water contact angle after approximately2000 to 3000 hours of such exposure. Indeed, the Examples illustratethat in the absence of a photocatalytic material the contact angle ofthe surface increased to nearly three times the initial contact angleafter exposure in a CCC for 3500 hours. Without being bound by any,theory, the inventors believe that this surprising result can beattributed to a partial crosslinking of the photocatalytic material withthe organosilicate which, yields Si—O—Ti bonds in the coating. Theinventors believe that some photocatalytic material takes part in suchcrosslinking, while some photocatalytic material remains available forphotocatalytic activation even after 4000 hours of CCC exposure.

In certain embodiments, coatings made from compositions of the presentinvention may maintain a contact angle of 5to 6 degrees after exposureto 650 hours in a Q-UV Tester equipped with fluorescent tubes (B313nanometers) at black panel temperature of 65° to 70° C. and 4 hourscondensing humidity at 50° C. atmosphere temperature.

Illustrating the invention are the following examples, which, however,are not to be considered as limiting the invention to their details.Unless otherwise indicated, all parts and percentages in the followingexamples, as well as throughout the specification, are by weight.

EXAMPLES Example 1 Preparation Of A Hydrolyzed Organosilicate Binder

An acid hydrolysis catalyst solution, referred to herein as solution“A”, was prepared by adding 7,000 grams of deionized water to a clean,dry 2 gallon container. With stirring, 1.0 gram of 70% nitric acid wasadded and set aside.

15.5 grams (˜0.10 moles) of 98% TMOS (tetramethoxysilane) representing˜6 grams of SiO₂ was added to a clean, dry 1 liter glass beaker. 3.6grams of solution A (˜0.20 moles of H₂O) was slowly added to the TMOS,controlling the exotherm by using an ice bath to maintain thetemperature below 25° C. Upon the completion of the addition of solutionA, this partially hydrolyzed silane solution was held for one hour at˜25° C. In a separate clean, dry beaker, 290.5 grams of ethanol and290.5 grams of deionized water were mixed and then added to the partial.hydrolyzate with stirring, after the one hour hold time. Then the pH ofthe diluted silane solution (pH˜5) was adjusted to pH˜3.9 by adding 0.80grams of glacial acetic acid with stirring. The resultant 1% SiO2 bindersolution was allowed to fully hydrolyze overnight with stirring.

Application on test panels with, above solution show good wetting withno optical flaws and passes 50 flood/dry cycles maintaining goodhydrophilicity.

Example 2 Preparation Of A Hydrolyzed Organosilicate Binder

15.5 grams (˜0.10 moles) of 98% TMOS representing ˜6-grams of SiO₂ and3.6 grams of anhydrous methanol (cosolvent) were added to a clean, dry 1liter glass beaker. 3.6 grams of solution A (˜0.20 moles of H₂O) wasslowly added to the TMOS solution, controlling the exotherm by the rateof addition of solution A. The peak temperature attained during theaddition was 33° C. Upon the completion of the addition of solution A,this partially hydrolyzed silane solution was held for one hour at ˜25°C. In a separate, clean, dry beaker, 287 grams of ethanol and 290.5grams of deionized water was mixed and then added to the partialhydrolyzate with stirring, after the one hour hold time. Then, the pH ofthe diluted silane solution (pH˜5) was adjusted to pH˜3.9by adding 0.80grams of glacial acetic acid with stirring. The resulting 1% SiO₂ bindersolution was allowed to fully hydrolyze overnight-with stirring.

Application on test panels with above solution show dewetting problemswith mottling. The test results suggest that the inclusion of cosolventprovided for a more efficient hydrolysis and corresponding condensationto form higher molecular weight oligomers which demonstrated theobserved behavior upon application.

Example 3 Preparation Of A Hydrolyzed Organosilicate Binder

15.5 grams (˜0.10 moles) of 98% TMOS (tetramethoxysilane) representing˜6 grams of SiO₂ was added to a clean, dry 1 liter glass beaker. 3.6grams of solution A (˜0.20 moles of H₂O) was slowly added to the TMOS,controlling the exotherm by the rate of addition of solution A. The peaktemperature attained during the addition was 40° C. Upon the completionof the. addition of solution A, this partially hydrolyzed silanesolution was held for one hour at ˜25° C. In a separate clean, drybeaker, 290.5 grams of ethanol and 290.5 grams of deionized water weremixed and then added to the partial hydrolyzate with stirring, after theone hour hold time. Then, the pH of the diluted silane solution (pH˜5)was adjusted to pH˜3.9 by adding 0.80 grams of glacial acetic acid withstirring. The 1% SiO2 binder solution was allowed to fully hydrolyzeovernight with stirring.

Application on test panels with above solution show dewetting problemswith mottling. The test results suggest that by not controlling theexotherm and allowing the temperature of the hydrolysis to reach ˜40°C., resulted in a much higher degree of condensation to form highermolecular weight oligomers which demonstrated the observed behavior uponapplication.

Example 4 Preparation Of A Hydrolyzed Organosilicate Binder

Methanol and deionized water were mixed at 1:1 (w:w) ratio understirring. The mixture was cooled to room temperature. 10.0 g of MS-51silicate solution (Mitsubishi Chemical Corporation, Tokyo, Japan) wascharged into a glass reactor, followed by addition of 504.8g f thepre-mixed methanol/water solvent mixture as one portion. The solutionwas stirred at 20-22 IC for 15 minutes. Then, 5.2 g of glacial aceticacid was added into the reactor under agitation. The solution mixturewas kept stirred at ambient for additional 24 hours. The final SiO₂content of the solution was 1% with a pH of 3.5.

Example 5 Preparation of A Hydrolyzed Organosilicate Binder

1-propanol and deionized water were mixed at 1:1 (w:w) ratio understirring. The mixture was cooled to room temperature. In a separatecontainer, acetic acid solution was prepared by diluting 10.0 g ofglacial acetic acid with 90.0 g of 1-propanol/water solvent mixture. 5.0g of MS-51 silicate solution was charged into a glass reactor, followedby addition of 253.7 9 of the pre-mixed 1-propanol/water solvent mixtureas one portion. The solution was stirred at 20-22° C. for 15 minutes.Then 1.4 g of pre-prepared acetic acid solution was added into thereactor under agitation. The solution mixture was kept stirred atambient for additional 24 hours. The final SiO₂ content of the solutionwas 1% with a pH of 4.1.

Example 6 Preparation of Liquid Compositions

Liquid compositions A through G in Table 1 were prepared as follows.Charge I was prepared in a one liter, glass vessel equipped with amagnetic stirrer. Charge I was prepared by adding the binder material tothe vessel and then adding deionized water to the vessel underagitation. The pH of the mixture was adjusted to 1.8 by adding 2Nhydrochloric acid under agitation until the desired pH was achieved.

Charge II was prepared in a 4 oz. glass container equipped with amagnetic stirrer. Titania sol was added to this vessel and the pH wasadjusted to 1.8 by adding 2N hydrochloric acid under agitation until thedesired pH was achieved. Charge II was then added under agitation toCharge I to produce the hydrophilic compositions A through G. TABLE 1Silicate/TiO₂ DI Titania Composition Weight Ratio Binder¹ Water Sol²Titania Sol³ A 0.5/0.3 500 g   480 g   20 g — B 0.5/0.3 500 g   480 g  20 g — C  0.4/0.24 40 g 58.4 g  1.6 g — D 0.31/0.19 31 g 67.7 g 1.27 g— E 0.25/0.25 25 g 73.3 g 1.67 g — F 0.9/0.1 47 g  2.3 g 0.33 g — G0.5/0.3 25 g 24.5 g — 0.5 g¹MSH-200 hydrolyzed organosilicate (1% solids) commercially availablefrom Mitsubishi Chemical Corporation, Tokyo, Japan.²NTB-1 titania sol commercially available from Showa Denko K.K., Tokyo,Japan.³STS-01 titania sol commercially available from Ishihara Sangyo KaishaLtd.

Example 7 Float Glass Test Substrates

The surface of 9″×12″ float glass test substrates were prepared bycleaning the substrate with a diluted Dart 210Solution (commerciallyavailable from Madison Chemical Co. Inc.) prepared by dilutingconcentrated Dart 210 with deionized water so that the solution had aconcentration of 5% to 10% Dart 210. The substrate was then rinsed withhot tap water and then deionized water. The test substrate was sprayedwith Windex® and wiped dry with a paper towel. (Kaydry® commerciallyavailable from Kimberly-Clark Corp.).

The liquid compositions of Example 6 were each applied to a testsubstrate by wipe application using a BLOODBLOC Protective Pad,commercially available from Fisher Scientific. The pad was wrappedaround the foam applicator. Then, 1.5 grams of the hydrophiliccomposition was applied to the pad using an eye dropper or plasticbottle with a dropper top. The compositions were then applied bycontacting the wet pad with the glass test substrate with straight,slightly overlapping strokes. After application, the substrates wasallowed to dry at room temperature for at least 2 prior to testing.Results are summarized in Table 2 TABLE 2 Ti PCA Surface ResistivityComposition (μg/cm²)¹ (cm⁻¹min⁻¹)² (ohms/cm²)³ Haze⁴ A 1.2 3.9 3.84 ×10⁹ 0.1% B 2.3 8.1 6.25 × 10⁸ 0.2% C 0.7 2.1 — — D 0.5 1.3 — — E 0.7 2.6— — F 0.4 0.6 — — G 1.9 5.5 — —¹Sample analyzed using X-ray fluorescence analysis.²Photocatalytic activity was evaluated as described in U.S. Pat. No.6,027,766 at col. 11, line 1 to col, 12, line 55.³Surface resistivity was evaluated with an ACL Statitide Model 800Megohmeter using either (1) large extension probes placed 5 millimetersapart at several locations on the sample, or (2) the meter's onboardprobes spaced 2¾ inches apart at several locations# on the sample.⁴Haze was evaluated with a Hazegard ® Model No. XL-211 haze meter,available from Pacific Scientific Company, Silver Spring, Md.

Durability Testing—Test 1

Test substrates coated with liquid compositions A and B were placed In aCleveland Condensation Chamber operating at 140° F. (60° C). Each testsubstrate was removed from the chamber weekly and tested to determinethe water contact angle. The photoactivity of the composition wasdetermined by measuring the water contact angle difference before andafter exposure of the substrate to UV light. The exposure interval was 2hours to a UVA-340 lamp supplied by the Q-Panel Company of Cleveland,Ohio or direct sunlight. The water contact angles reported were measuredby the sessile drop method using a modified captive bubble indicatormanufactured by Lord Manufacturing, Inc., equipped with GartnerScientific goniometer optics. The surface to be measured was placed in ahorizontal position, facing upward, in front of a light source. Asessile drop of water was placed on top of the surface in front of thelight source so that the profile of the sessile drop could be viewed andthe contact angle measured in degrees through the goniometer telescopewhich is equipped with circular protractor graduations. Results aresummarized in Table 3. TABLE 3 Composition A Contact Composition B AngleContact Angle Contact Angle Contact Angle Hours in Before After BeforeAfter CCC Exposure Exposure Exposure Exposure 0 20 3 12 3 498 14 3 12 31062 38 3 37 3 1535 32 3 27 3 2221 18 4 9 3 2573 30 3 26 3 2975 30 5 334 3565 — — 30 5 4040 — — 19 4

Durability Testing—Test 2

The durability of test substrates coated with liquid compositions Athrough G was tested by measuring the water contact angle after exposureto UV light as described above but prior to placement in the ClevelandCondensation Chamber. The same substrates were then placed, in the CCCas described above for at least 4000 hours and then removed. Thesubstrates were then exposed to UV light as described above and testedby measuring the water contact angle. Results are summarized in Table 4.TABLE 4 Contact Angle Before CCC Contact Angle After CompositionExposure 4000 Hours CCC A 3 5 B 3 4 C 5 4 D 5 3 E 6 2 F 5 9 G 3 3

Durability Testing—Test 3

The durability of test substrates coated with compositions of thepresent invention was also compared to substrates coated withcompositions comprising hydrophilic organosilicate binder but no thephotocatalytic material. Hydrophilic compositions B and F of Example 6as well as a similar composition having a binder to titanium dioxideratio of 0.95/0.5 (composition J),were placed in the ClevelandCondensation Chamber as described above a periodically removed andexposed to UV light as described above. Comparative composition A wasShinsui Flow MS-1200, available from Dainippon Shikizai, Tokyo, Japanand comparative composition B was MSH-200, available from MitsubishiChemical Corporation, Tokyo, Japan. The test substrates were tested forwater contact angle as described above. Results are illustrated in FIG.4.

Example 8 Preparation of Liquid Compositions

Liquid compositions H and I were prepared in the manner described inExample 1 except that WINDEX was included in the composition in theamount identified in Table 5 and the Binder/TiO₂Weight Ratio was as setforth in Table 5. The durability of these compositions was then analyzedin the manner described in Durability Testing—Test 1. Results are setfourth in Table 6. TABLE 5 Silicate/TiO₂ Amount of Amount of CompositionWeight Ratio Binder/TiO₂ ¹ WINDEX H 0.35/0.25 30 g 8.91 g I 0.35/0.25 30g 6.26 g

TABLE 6 Composition H Composition I Contact Contact Contact ContactHours in Angle Before Angle After Angle Before Angle After CCC ExposureExposure Exposure Exposure 0 4 4 5 4 330 27 2 21 2 834 19 2 31 2 2390 263 23 5 3374 18 3 16 3 4022 38 4 32 11

Example 9 Turbidity of Liquid Compositions

Liquid compositions K, L, M, and O were prepared in the manner describedin Example 6 except that the pH was adjusted to the value set forth inTable 7 and the Binder/TiO₂Weight Ratio was as adjusted as set forth inTable 7. Liquid compositions N, P, and Q were prepared in a mannersimilar to Example 6, except that the pH of Charge I was not adjusted,and Charge II was a mixture of the titania sol and deionized water in anamount sufficient to dilute the titania sol from 15% solids to 2% solidswith deionized water. The pH of Charge II was not adjusted and Charge IIwas added to Charge I to make the liquid composition. The turbidity ofthese compositions was then analyzed over time by a Turbidimeter, ModelDRT-100D. manufactured by Shaban Manufacturing Inc, H. F. InstrumentsDivision using a sample cuvette of 28 mm diameter by 91 mm in lengthwith a flat bottom. Results are set forth in Table 7. TABLE 7 Turbidity(NTU) Silicate/TiO₂ 1 3 6 Composition Weight Ratio pH Initial monthmonths months K 0.5/0.3 1.96 490 558 569 652 L 0.5/0.3 1.57 438 552 567653 M 0.35/0.2  1.8 321 383 393 442 N 0.35/0.2  3.25 454 412 385 425 O 0.4/0.25 1.8 415 488 511 573 P 0.5/0.1 3.1 145 143 145 153 Q 0.9/0.13.11 149 143 145 162

Example 10 Fogging Resistance On A Plastic Lens

This example is intended to illustrate the anti-fogging properties ofthe present invention. Thermoplastic polycarbonate lenses that werepreviously coated by the supplier with a non-tintable hardcoat (Gentex®PDQ®, commercially available from Gentex Optics, Inc.) were surfacetreated by washing with soap and water, rinsing with deionized water andiso-propyl alcohol, and air drying. The lenses were then plasma treated.For example, 10A no additional coating was applied to the lens. Forexample 10B, the plasma-surface treated lens was coated with MSH-200hydrolyzed organosilicate (1%. solids) commercially available fromMitsubishi Chemical Corporation, Tokyo, Japan. For Example 10C, theplasma-surface treated lens was coated with a composition of the typedescribed in Example 6, composition E by dip coating at an extractionrate of 230 mm/min.

Fogging property was evaluated by placing the lens over a cup filledwith hot water. The lens of Example 10A fogged over the entire areathereof. The lens of Example 10B fogged over 50-60% of the area thereof.The lens of Example 10C has not fogging on the surface thereof.

Example 11 Resistance to Fouling by Automotive Break Dust

This Example is intended to illustrate the anti-fouling properties ofthe present invention. Two aluminum alloy wheels purchased fromDaimlerChrysler were divided into five even areas using masking tape.The wheels were installed on a 1996 model Chrysler Jeep Cherokee withone wheel (wheel #1) being installed on the front passenger side, andthe other wheel (wheel #2) being installed on the front driver's side.Prior to installation, the five areas, of each of wheel #1 and wheel #2were treated as follows.

Wheel #1 Preparation

Prior to installation on the vehicle, the five areas of wheel #1 weretreated as follows. No coating was applied to Area 1. Area 2 was coatedwith Hi-Gard ™1080 (an organosilane-containing coating solutionavailable from PPG Industries, Inc.) by curtain coating using a washbottle, air drying for 5 minutes, and the baking at 240° F. (116° C.)for 3 hours. Area 3 was coated with Hi-Gard 1080 as described above forArea #2. After baking, Area 3 was then coated with MSH-200 hydrolyzedorganosilicate (1% solids) commercially available from MitsubishiChemical Corporation, Tokyo, Japan by wipe on application with a soakedsponge. The MSH-200 was then allowed to air dry and self-condense. Area4 was coated with Hi-Gard 1080 as described above for Area 2. Afterbaking, Area 4 was coated with a composition of the type described inExample 6, composition E and a mixture of deionized water and ethanol(50/50 weight ratio) by using a soaked sponge. Area 5 was coated with acomposition of the described in Example 6, composition E.

The vehicle was driven for one week. Areas 1 through 5 of wheel #1showed no significant difference in cleanliness prior to a water rinse.After being rinsed with water from a garden hose, the cleanliness ofAreas 1 to 5 of wheel #1 was measured on a scale of 1 to 10 with highernumber reflecting a cleaner surface. The results are summarized in Table8. TABLE 8 Area Cleanliness 1 2 2 6 3 8 4 10 5 10

Wheel #2 Preparation

Prior th installation on the vehicle, the five areas of wheel #2 weretreated as follows. No coating was applied to Area 1. Area 2 was coatedwith SolGard®330 coating (an organosilane-containing coating solutionavailable from PPG Industries, Inc.) by curtain coating using a washbottle, air drying for 5minutes, and the baking at 240° F. (116° C.) for3 hours. Area 3 was coated with Hi-Gard 1080 as described above for Area2. After baking, Area 3 was then coated with MSH-200 hydrolyzedorganosilicate (1% solids) commercially available from MitsubishiChemical Corporation, Tokyo, Japan by wipe on application with a soakedsponge. The MSH-200 was then allowed to air dry and self-condense. And 4was coated with Hi-Gard 1080 as described above for Area 2. After baking,Area 4 was coated with a composition of the type described in Example6,composition E and a mixture of deionized water and ethanol(50/50weight ratio) by wipe-on application using a soaked sponge. Area 5was coated with a composition of the type described in Example 6,composition E. The vehicle was driven for one week. Areas 1 through 5 ofwheel #1 showed no significant difference in cleanliness prior to awater rinse. After being rinsed with water from a garden hose, thecleanliness of Areas 1 to 5 of wheel #1 was measured on a scale of 1 to10 with higher number reflecting a cleaner surface. The results aresummarized in Table 9. TABLE 9 Area Cleanliness 1 2 2 8 3 10 4 10 5 10

Examples 12A and 12B Application to Painted Surface.

Example 12A: A liquid composition was prepared by adding three grams ofSurfynol 465 (available from Air Products) to 100 grams of a liquidcomposition of the type described in Example 6, composition E andstirring the mixture

Panel Preparation

Aluminum panels, pre-treated with Betz Permatreat 1500, were coated withTruform® ZT high gloss white polyester coating (available from PPGIndustries, Inc) by using a wire wound drawdown bar at 0.7-0.8 mil dryfilm thickness. The coated aluminum panel was baked at 450° F. (peakmetal temperature) for 30seconds. For Example 12(1), no additionalcoating was added. For Example 12(2), the above prepared hydrophiliccomposition was applied over Truform ZT-painted aluminum panel by usingwire wound drawdown bar at 0.05-0.15 mil dry film thickness. The panelwas baked at 350° F.(peak metal temperature) for 25 seconds.

Exposure Test Results

Coated panel and un-coated panels were compared after six months inMalaysia. Results are set forth in Table 10. TABLE 10 6 Months Malaysia3 months south Florida Position of Panel: horizontal Position of panel:45° south Example Unwashed ΔL¹ Washed ΔL Unwashed ΔL Washed ΔL 12(1)−21.6 −13.82 −6.05 −4.02 12(2) −8.30 −1.00 −3.35 −0.01¹Lightness (L) was determined using a MacBeth Color Eye ® 2145Spectrophotometer, available from the Macbeth division of KollmorgenInstruments. Lightness measurements were taken before and after exposuretesting and the difference (dL)# recorded. A dL value closer to zero (positive or negative) indicatesbetter performance. A low ΔL value means less color change. A negativevalue means the coating got darker color comparing to the original colorreading. A low Δ in un-washed area would # indicate that the panel wasless dirty without washing.

Example 12B: Aluminum panels, pre-treated with Betz Permatreat 1500,were coated with Duranar® Semi Gloss coating (available from PPGIndustries, Inc.) in a manner similar to that described in Example 12A.

For Example 12(3), the liquid composition described in Example 12A wasapplied over the Duranar painted aluminum panel by using wire wounddrawdown bar at 0.05-0.15 mil dry film thickness. The panel was baked at350° F. (peak metal temperature) for 25 seconds. For Example 12(4),Toto. Frontier Research Co., Ltd. finished the painted panel withtitanium dioxide-containing low maintenance clearcoat. The panels ofExamples 12(3) and 12(4) were exposed at South Florida for 13 month and14 months. Cracking was observed on the panel of Example 12(4) and nocracking was observed on the panel of Example 12(4).

Example 13 Application to Millwork Substrate

Sample preparation: Control samples were lab generated or commercialproduction panels finished with a commercial solventborne polyurethanemillwork coating. Test parts were prepared by first wiping the partswith isopropanol. Next, liquid compositions of the type described inExample 6, composition E were applied by lightly wiping a soaked papercloth over the part. Coatings were air dried overnight. Samples wereprepared over four substrates; phenolic paper clad door substrate (FWD),fiberglass pultrusion (pult), vinyl-clad fiberglass pultrusion (VCP),and pine window substrate (NLP). Samples were sent to an exposure sitein Malaysia for three months exposure prior to being returned andevaluated for color change and gloss retention. Results are set forth inTable 11. TABLE 11 Substrate NLP FWD Pult. VCP Example Example ExampleExample Sample Control 7A Control 7B Control 7C Control 7D Color change14.3 8.9 12.7 4.7 16.4 2.7 10.8 2.3 % Gloss 54 47 76 108 69 87 71 71Retention

It will be readily appreciated by those skilled in the art thatmodifications may be made to the invention without departing from theconcepts disclosed in the foregoing description. Such modifications areto be considered as included within the following claims unless theclaims, by their language, expressly state otherwise. Accordingly, theembodiments described in detail herein are illustrative only and are notlimiting to the scope of the invention, which is to be given the fullbreadth of the appended claims and any and all equivalents thereof.

1. A liquid composition comprising: (a) a photocatalytic material, and(b) a hydrophilic binder comprising an essentially completely hydrolyzedorganosilicate.
 2. The liquid composition of claim 1 wherein at leastapportion of the photocatalytic material is present in the form ofparticles having an average crystalline diameter of 3 to 35 nanometers.3. The liquid composition of claim 1, wherein the photocatalyticmaterial is selected from the group consisting of the brookite form oftitanium dioxide, titanium dioxide chemically modified by flamepyrolysis, nitrogen doped titanium dioxide, plasma treated titaniumdioxide, and mixtures thereof.
 4. The liquid composition of claim 1,wherein the photocatalytic material is provided in the form of a solcomprising particles of photocatalytic material dispersed in water. 5.The liquid composition of claim 1, wherein the photocatalytic materialis present in the liquid composition in an amount ranging from 0.1 to0.75 percent by weight based on the total weight of the composition. 6.The liquid composition of claim 1, wherein the organosilicate isselected from the group consisting of organoxysilanes,organoxysiloxanes, and mixtures thereof, wherein the organoxysilanes areselected from the group consisting of tetramethoxysilane,tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane,tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane,tetra-t-butoxysilane, tetraphenoxysilane, dimethoxydiethoxysilane, andmixtures there of.
 7. The liquid composition of claim 1, wherein theorganosilicate is present in the liquid composition in an amount rangingfrom 0.1 to 2 percent by weight calculated as SiO₂, based on the totalweight of the composition.
 8. The liquid composition of claim 1, whereinthe photocatalytic material and the organosilicate are present in theliquid composition at a ratio of 0.05:0.95 to 5:0.3 by weight.
 9. Theliquid composition of claim 1, wherein the pH of the composition is nomore than 3.5.
 10. The liquid composition of claim 1, wherein the pH ofthe composition is from 7.0 to 8.5.
 11. A substrate coated with a curedfilm formed from the liquid composition of claim
 1. 12. The substrate ofclaim 11, wherein the film has a dry film thickness of 20 to 60nanometers.
 13. The substrate of claim 11, wherein the film exhibits aninitial water contact angle, of no more than 10° prior tophotoexcitation of the photocatalytic material.
 14. The substrate ofclaim 11, wherein, following excitation of the photocatalyst, the filmexhibits a water angle with water of less than 5°.
 15. A method formaking the liquid composition of claim 1, the method comprising thesteps of: (a) providing a hydrophilic material comprising an essentiallycompletely hydrolyzed organosilicate, wherein the pH of the hydrophilicmaterial is no more than 3.5; (b) providing a sol or paste comprising aphotocatalytic material dispersed in a diluent, wherein the pH of thesol or paste is no more than 3.5; and (c) mixing the hydrophilicmaterial provided in (a) with the sol or paste provided in (b) todisperse the photocatalytic material in the hydrophilic material. 16.The method of claim 15, wherein the hydrophilic material provided instep (a) is obtained by (1) providing a hydrophilic material comprisingan essentially completely hydrolyzed organosilicate, wherein the pH ofthe hydrophilic material is greater than the desired pH, and (2) addingacid to the hydrophilic material until the desired pH is achieved. 17.The method of claim 15, wherein the sol or paste provided in step (b) isobtained by (1 )providing a sol or paste comprising a photocatalyticmaterial dispersed in a diluent, wherein the pH of sol or paste isgreater than the desired pH, and (2) adding acid to the sol or pasteuntil the desired pH is achieved.
 18. A method for making the liquidcomposition of claim 1, the method comprising the steps of: (a)providing a hydrophilic material comprising an essentially completelyhydrolyzed organosilicate, wherein the pH of the hydrophilic material isfrom 7.0to 8.5; (b) providing a sol or paste comprising a photocatalyticmaterial dispersed in a diluent, wherein the pH of the sol or paste isfrom 7.0 to 8.5; and (c) mixing the hydrophilic material provided in (a)with the sol or paste provided in (b) to disperse the photocatalyticmaterial in the hydrophilic material.
 19. The method of claim 18,wherein the hydrophilic material provided in step (a) is obtained by (1) providing a hydrophilic material comprising an essentially completelyhydrolyzed organosilicate, wherein the pH of the hydrophilic material isless than the desired pH, and (2) adding a base to the hydrophilicmaterial until the desired pH is achieved.
 20. The method of claim 18,wherein the sol or paste provided in step (b) is obtained by (1)providing a sol or paste comprising a photocatalytic material dispersedin a diluent, wherein the pH of sol or paste is less than the desiredpH, and (2) adding a base to the sol or paste until the desired pH isachieved.
 21. The liquid composition of claim 1, wherein the liquidcomposition is in the form of a one-pack liquid composition having ashelf-life of at least 3 months.
 22. The composition of claim 21,wherein the one-pack liquid composition has a shelf-life of at least 6months.
 23. The composition of claim 22, wherein the one-pack liquidcomposition has a shelf-life of at least 12 months.
 24. The compositionof claim 23, wherein the composition has a turbidity of no more than 600NTU after 3 months.
 25. A method of coating a substrate comprising thesteps of: (a) applying to the substrate the liquid composition of claim1, and (b) curing the composition.
 26. The method of claim 25, whereinthe composition is cured by exposing the composition to air for at leasttwo hours at 25° C.
 27. The liquid composition of claim 1, wherein thephotocatalytic material is present in the liquid composition in anamount sufficient to produce a coating that maintains its initial watercontact angle after exposure to a Cleveland Condensation Chamber for4000 hours, wherein the CCC chamber is operated at a vapor temperatureof 140° F. (60° C.) in an indoor ambient environment which results inconstant water condensation on the test surface.
 28. The liquidcomposition of claim 1, wherein the photocatalytic material is presentin the liquid composition in an amount sufficient to produce a coatingthat maintain a contact angle of less than 10 degrees after exposure toa Cleveland Condensation Chamber for 4000 hours, wherein the CCC chamberis operated at a vapor temperature of 140° F. (60° C.) in an indoorambient environment which results in constant water condensation on thetest surface.
 29. The liquid composition of claim 1 , wherein the binderis prepared by a process selected from: (a) a multi-stage processcomprising a first stage wherein a partial hydrolysis polycondensationreaction product is formed by reacting an organosilicate water in thepresence of an acid hydrolysis catalyst, wherein the water is present inan amount that is less than the stoichiometric amount capable ofhydrolyzing the organoxy groups of the organosilicate, and a secondstage wherein the partial hydrolysis polycondensation reaction productis contacted with a large amount of water to form an essentiallycompletely hydrolyzed organosilicate, and (b) reacting atetraalkoxysilane oligomer with water in the presence of an organic acidhydrolysis catalyst and/or an organic solvent, wherein the water ispresent in an amount that is considerably greater than thestoichiometric amount capable of hydrolyzing organoxy groups of thealkoxysilane to form an essentially completely hydrolyzedorganosilicate.
 30. The liquid composition of claim 29, wherein thebinder is prepared by the multi-stage process.
 31. The liquidcomposition of claim 30, wherein the water is present during the firststage in a stoichiometric amount capable of hydrolyzing 50 percent ofthe organoxy groups of the organosilicate.
 32. The liquid composition ofclaim 30, wherein the first stage is conducted at conditions that limitthe degree of condensation of Si—OH groups formed as a result of thehydrolysis reaction.
 33. The liquid composition of claim 32, wherein theconditions that limit the degree of condensation of Si—OH groups formedas a result of the hydrolysis, reaction are selected from controllingthe reaction exotherm by external cooling, controlling the rate ofaddition of the acid catalyst, and/or conducting the first stagehydrolysis in the substantial absence of any organic cosolvent.